Topic: cb550f running at 10mpg

[Bru-tom]

Hey guys, after 3 years of sitting in storage i managed to get her back into shape for the DGR this year.

all the old quirks from yesteryear are all back, like they were going to disappear, right?!

i know my carbs are 100% spot on, i am very pedantic about things like that, rebuilt, stock jets and needle position and synchronized. i am running a 4-1 and custom filter with correct flow etc. The filter is a custom design so before you guys ask about flow etc, the bike still bellows black smoke out even without the filter installed 

Anyway, i remember dressing the points before the bike stood, so i assumed that they were still fine.... On Friday, i decided to do static timing, the 1-4 was a little advanced and the 2-3 a little more so...no idea how they came to be so far out. so i adjusted and set to "F" on both and took the bike for a ride on brand new plugs. The intention was to stop and check them after the point where i always experience the burble and bucking of the bike, probably just off idle and about 1/8 throttle, everywhere else she hauls ass. i rode 1km, and pulled the plugs and they were black and sooty as ever, all 4 even worse than before. i decided to still go for a bit of a ride but when i was about 20km from home, the bike would cut out every time i came to a stop, while bellowing black smoke out the exhaust.

As soon as i arrived home, i decided to advance the timing again, probably 3mm advanced from the "F". she idled erratically but absolutely no smoke when rev'd a little where before she would puff black smoke out the exhaust. i decided to gap the points; until i saw major pitting. Way worse than i found them when i first dressed them. I am very particular with certain things and i was sure to have done them properly the first time, say 1000km before i parked it. i dressed them again and i can barely make the "F" timing mark on 2-3, so they have to be replaced.

I am ordering a complete points plate with points and condenser from DSS. My question is, could the ignition system have been the culprit from my rich condition since the beginning??

[Deltarider]

Yep, the condensers could...

[Bru-tom]

Yep, the condensers could...

but why only at the throttle position, off idle?

[Deltarider]

...no idea how they came to be so far out.

How about breakerpoints gap that has changed?
Intermittent grounding breakerpoints (when they shouldn't) and faulty condensers also could cause problems.
In case you have the stock ignition setup, I'd first check breakerpoints and condensers. Open the ignition cover. First check if breakerpointgap is still correct and also that the forked connectors at the back of the breakerpoints aren't accidently touching the plate. Then, with engine running, see if there's excessive arcing at the breakerpoints. A tiny bit of sparking is normal, excessive sparking is not good. See

In this vid left condensor (1+4) is bad, right condensor (2+3) is good.

[TwoTired]

If the mixture fires, it had ignition.  If it has too much fuel in the mix, it will leave black deposits due to incomplete burn.
Misfires are usually quite noticeable during a drive about.

What is the actual fuel level in the float bowls?
Have your jets been drilled?
Are you operating the choke backwards?
Are the main jets still in their seats?  Is the spring retainer still in place?
Are the main jet reception posts pitted enough to prevent the oring from sealing?

Explain how you know you have "stock jets and needles".

Cheers,

[Bru-tom]

If the mixture fires, it had ignition.  If it has too much fuel in the mix, it will leave black deposits due to incomplete burn.
Misfires are usually quite noticeable during a drive about. you are correct, when i retarded the timing, the bike became even more rich and started misfiring because the plugs were sooted up good and properly.

What is the actual fuel level in the float bowls? 22mm. i have not used the clear tube method as of yet to identify the actual level unfortunately.
Have your jets been drilled? i hope not, i got them from harisluv.
Are you operating the choke backwards? with the choke closed/on, it dies immediately.
Are the main jets still in their seats?  Is the spring retainer still in place? yes, everything is brand new, sealed and in place.
Are the main jet reception posts pitted enough to prevent the oring from sealing? there is pitting on the outside on the post, not inside.

Explain how you know you have "stock jets and needles". they are 38 idles and 100 mains. needles are new secondhand from harisluv, i can still see the lath turning pattern on the needle and it is in mint condition. my old jets and needles cause the bike to behave in the same manner, which is why i went through the mission of importing original jets.

Cheers,

[Bru-tom]

...no idea how they came to be so far out.

How about breakerpoints gap that has changed?
Intermittent grounding breakerpoints (when they shouldn't) and faulty condensers also could cause problems.
In case you have the stock ignition setup, I'd first check breakerpoints and condensers. Open the ignition cover. First check if breakerpointgap is still correct and also that the forked connectors at the back of the breakerpoints aren't accidently touching the plate. Then, with engine running, see if there's excessive arcing at the breakerpoints. A tiny bit of sparking is normal, excessive sparking is not good. See

In this vid left condensor (1+4) is bad, right condensor (2+3) is good.

thank you sir. i have checked the gaps and had to dress them. After that i had to reset the timing. i barely can set the 2-3 on the"f" mark now. but its there. bike still runs rich.

i will have a look and see if i can find excessive sparking during this week and give feedback. the points are very pitted, i had to take a lot off to even try get them barely usable.

can the condensers cause a weak spark and allow the fuel mixture not to ignite properly?

[Deltarider]

can the condensers cause a weak spark and allow the fuel mixture not to ignite properly?

Yes, they can. Sometimes condensers start sputtering when warm. That your points are badly pitted, to me indicates there's arcing. Unless the forked connector is intermittent making contact with the baseplate, usually the condenser is to blame. Easy fix and not expensive. Some say you should stay away from aftermarket condensers. I myself have no experience with them, so I can't tell.   

[TwoTired]

Do all your plugs exhibit the same deposit pattern?

You have two condensers.  Rare they would both fail at the same time in the same way.  However, some manufacturing defects can be that way.

Did you replace the float valve needles/seats?  Did you notice if the little spring pins had the same strength as originals?

Have you cleared and proven the air jets and their passageways? Two per carb.

Cheers,

[Bru-tom]

can the condensers cause a weak spark and allow the fuel mixture not to ignite properly?

Yes, they can. Sometimes condensers start sputtering when warm. That your points are badly pitted, to me indicates there's arcing. Unless the forked connector is intermittent making contact with the baseplate, usually the condenser is to blame. Easy fix and not expensive. Some say you should stay away from aftermarket condensers. I myself have no experience with them, so I can't tell.

thank you kindly.

what is this forked connector you speak of? is it the wire terminal that connects to the points? i have however ordered a complete backing plate, condensers and points from David Silver Spares. 

[Bru-tom]

Do all your plugs exhibit the same deposit pattern?

You have two condensers.  Rare they would both fail at the same time in the same way.  However, some manufacturing defects can be that way.

Did you replace the float valve needles/seats?  Did you notice if the little spring pins had the same strength as originals?

Have you cleared and proven the air jets and their passageways? Two per carb.

Cheers,

all of the plugs are identical. i was hoping to see either the 1-4 or 2-3 to be different, but they were not.

i replaced on needle and seat. the needle sprung pin was not sprung any more, so i replaced it. the new spring is a little stiffer than the rest. i can understand that the stiffer spring will cause the fuel to get cut off sooner than the rest, how would one compensate for it? clear tube test?

yes, they are spotless, i used an ultrasonic bath mixed with carb cleaner and compressed air. everything is perfect iv done this procedure several times in the past when i had the same issues, thats when i replaced jets etc from harisluv....

[carnivorous chicken]

Just to throw in an unsolicited 2 cents -- if you are truly getting 10mpg there has to be something more than a rich running condition. You should be getting about 4X that. I would think (if 10mpg is true) that there is no way that thing would run and you might want to check that gas isn't pouring out of your overflows (if you have lines connected that drop to the ground it'd be harder to notice when riding as the gas wouldn't be spilling onto your engine). And if they are overflowing, you're going to be running rich as well.

[Bru-tom]

Just to throw in an unsolicited 2 cents -- if you are truly getting 10mpg there has to be something more than a rich running condition. You should be getting about 4X that. I would think (if 10mpg is true) that there is no way that thing would run and you might want to check that gas isn't pouring out of your overflows (if you have lines connected that drop to the ground it'd be harder to notice when riding as the gas wouldn't be spilling onto your engine). And if they are overflowing, you're going to be running rich as well.

thank you kindly for your input.

i use metric measuring system and used a google converter. i get 5km per litre and converted in like 11mpg.

i have no leaks, my bike is in my lounge on porcelain tiles, i know for sure there are no leaks. i did find a crack in one of my brass overflow tubes that i soldered, but no leaks this far. i was confident enough to not even put overflow tubes on the bowls lol.

[TwoTired]

all of the plugs are identical. i was hoping to see either the 1-4 or 2-3 to be different, but they were not.

What are the numbers on the Jet needles?  And what clip position did you select?
Also, have you checked the emulsion tube jet exit for size and damage?  This is where the needles regulate flow.

i replaced on needle and seat. the needle sprung pin was not sprung any more, so i replaced it. the new spring is a little stiffer than the rest. i can understand that the stiffer spring will cause the fuel to get cut off sooner than the rest, how would one compensate for it? clear tube test?

Yes. The spring stiffness changes the mechanical float height measurement.

yes, they are spotless, i used an ultrasonic bath mixed with carb cleaner and compressed air. everything is perfect iv done this procedure several times in the past when i had the same issues, thats when i replaced jets etc from harisluv....

Just to be clear.  You verified flow from air jet entry to emulsion tube cavity for both the pilot circuit and the main emulsion tube?  A cleaning process is not complete until this has been done.  Please don't just assume.

Just to be thorough, state condition of the carb couplers, and if you have disturbed the manifold to head connection orings.

Would you expect your replacement exhaust to have more or less backpressure than the original?

Cheers,

[Bru-tom]

What are the numbers on the Jet needles?  And what clip position did you select?
Also, have you checked the emulsion tube jet exit for size and damage?  This is where the needles regulate flow.

i can not recall, i am getting a new set of carb to intake boots soon, making it easier to remove the carbs to recheck everything. i am not excited 

i have not checked the emulsion tube exit, i will check my old needles for wear and if there is little to no wear, then i can assume there is little to none on the emulsion exit, takes two to tango

Yes. The spring stiffness changes the mechanical float height measurement.

i will have to do the clear tube method of setting them up then. In the past, i did change the float height levels in increments of 1mm all the way up to 25mm, nothing changed, still same rich conditions.

Just to be clear.  You verified flow from air jet entry to emulsion tube cavity for both the pilot circuit and the main emulsion tube?  A cleaning process is not complete until this has been done.  Please don't just assume.

Just to be thorough, state condition of the carb couplers, and if you have disturbed the manifold to head connection orings.

Would you expect your replacement exhaust to have more or less backpressure than the original?

Cheers,

ye sir, immaculately clean. my father was a watch maker, lets say i took a feather out his cap

the carb couplers have been lubricated with a tiny smear of lithium grease on them. i sprayed carb cleaner on the vaccuum ports and intake manifolds where they meet the head, no leaks there...

if anything, the new exhaust is less restrictive. its only just though...

[05c50]

You stated "i know my carbs are 100% spot on", but then continued to describe a problem that most likely is a carb problem. Without knowing the actual level of the fuel in the bowls, it's hard to know that the carbs are spot on. You are not the first to report this exact problem on a 550F, look at this thread (there are others) http://forums.sohc4.net/index.php/topic,174062.msg2025561.html#msg2025561   It's very difficult to see the inside of the emulsion tubes and even harder to determine if they're good or bad.

........Paul

[tlbranth]

FWIW, when I first cobbled my 750 together after a 25 year layoff, I was getting 17mpg, constant burbles and lousy power. First thing I did was chuck the coils and install Dyna coils, plug wires and new plug caps. Then I found that the air filter I was using was running me waaaay rich so I put in an OEM filter. Things improved radically but not quite where I'd liked. I was still running rich. I lowered my needles 1 notch and things improved a lot. It's still not the way it was out of the showroom in 1970 but it's pretty darn good. I'm getting close to 50mpg and the bike runs great. Idle is only good after the engine is good and hot.
Don't look for a silver bullet. There isn't one. It's a matter of messing with things to gain a bit of improvement 'til you're happy with it.

[Deltarider]

what is this forked connector you speak of? is it the wire terminal that connects to the points?

Yes. See to it that it can not (intermittently) contact the base plate. The 2+3 breaker in particular is prone to this as there's a crosshead nearby.

[Bru-tom]

You stated "i know my carbs are 100% spot on", but then continued to describe a problem that most likely is a carb problem. Without knowing the actual level of the fuel in the bowls, it's hard to know that the carbs are spot on. You are not the first to report this exact problem on a 550F, look at this thread (there are others) http://forums.sohc4.net/index.php/topic,174062.msg2025561.html#msg2025561   It's very difficult to see the inside of the emulsion tubes and even harder to determine if they're good or bad.

........Paul

spot on, as in all stock, crystal clean and synchronized. i will confirm the float levels when i get my spares next week. I did mention that i adjusted the float levels way higher than stock which didnt help a thing in the past. I have been reading and reading for weeks now. most people sort things out with dirty emulsion tubes, but i do not have a dirty carb issue, i hope its related to my ignition timing, because as soon as i advanced the timing a little, the richness at idle, when normally with a little rev would bellow black smoke out the exhaust, was gone. my points need to be replaced, those bits are coming, so i will have o take the next step then i guess...just trying to eliminate one thing at a time and im tired of pulling carbs on and off all the time. if the fueling is still off thereafter the timing is sorted, then i will have to start fiddling with the carbs one more...

where can i get new oem emulsion tubes?

[Bru-tom]

FWIW, when I first cobbled my 750 together after a 25 year layoff, I was getting 17mpg, constant burbles and lousy power. First thing I did was chuck the coils and install Dyna coils, plug wires and new plug caps. Then I found that the air filter I was using was running me waaaay rich so I put in an OEM filter. Things improved radically but not quite where I'd liked. I was still running rich. I lowered my needles 1 notch and things improved a lot. It's still not the way it was out of the showroom in 1970 but it's pretty darn good. I'm getting close to 50mpg and the bike runs great. Idle is only good after the engine is good and hot.
Don't look for a silver bullet. There isn't one. It's a matter of messing with things to gain a bit of improvement 'til you're happy with it.

thank you sir, i will start with my points and timing, then move onto perhaps replacing the coils. apparently a good mod is to use GL1000 coils. thanks, there is still hope for mine yet

https://www.motorcycleproject.com/text/sohcign.html

[Bru-tom]

Yes. See to it that it can not (intermittently) contact the base plate. The 2+3 breaker in particular is prone to this as there's a crosshead nearby.

thank you. but why would all four suffer from this, all the plugs are black i will make sure that these are insulated properly when i install the new ignition soon.

[Bru-tom]

Here is the bike after months of cleaning, servicing for the distinguished ride two weeks ago








Sent from my iPhone using Tapatalk

[Deltarider]

Yes. See to it that it can not (intermittently) contact the base plate. The 2+3 breaker in particular is prone to this as there's a crosshead nearby.

thank you. but why would all four suffer from this, all the plugs are black i will make sure that these are insulated properly when i install the new ignition soon.

How about the airfilter? Any restriction in the air intake? BTW, if you go the GL1000 coils route, you will need a ballast resistor of say 2 Ω or your points will pit severely.

[tlbranth]

Good call on the 1000 coils. Better would be GL1500 coils. Modern, reliable and you can get 3 for a song.
I had a brand new, ill-fitting Emgo air filter. If you have one, throw it in the neighbor's yard and get an OEM. Night and day.

[Bru-tom]

Yes. See to it that it can not (intermittently) contact the base plate. The 2+3 breaker in particular is prone to this as there's a crosshead nearby.

thank you. but why would all four suffer from this, all the plugs are black i will make sure that these are insulated properly when i install the new ignition soon.

How about the airfilter? Any restriction in the air intake? BTW, if you go the GL1000 coils route, you will need a ballast resistor of say 2 Ω or your points will pit severely.

My filter set up is a custom one. I have modified the plenum intake to house a custom filter box. I have removed it entirely and there is no change in this rich condition the surface area is exactly the same as original, so with no filter attached it should break just as well as the original setup would....